1. Field of Disclosure
This invention relates to near field RF communicators and near field communications enabled devices.
2. Related Art
Near field RF (radio frequency) communication is becoming more and more commonplace as is the use of such technology to transfer data. Near field RF communicators communicate through the modulation of the magnetic field (H field) generated by a radio frequency antenna. Near field RF communication thus requires an antenna of one near field RF communicator to be present within the alternating magnetic field (H field) generated by the antenna of another near field RF communicator by transmission of an RF signal (for example a 13.56 Mega Hertz signal) to enable the magnetic field (H field) of the RF signal to be inductively coupled between the communicators. The RF signal may be modulated to enable communication of control and/or other data. Ranges of up to several centimeters (generally a maximum of 1 meter) are common for near field RF communicators.
NFC communicators are a type of near field RF communicator that is capable in an initiator mode of initiating a near field RF communication (through transmission or generation of an alternating magnetic field) with another near field RF communicator and is capable in a target mode of responding to initiation of a near field RF communication by another near field RF communicator. The term “near field RF communicator” includes not only NFC communicators but also initiator near field RF communicators such as RFID transceivers or readers that are capable of initiating a near field RF communication but not responding to initiation of a near field RE communication by another near field RF communicator and target or responding near field RF communicators such as RFID transponders or tags that are capable of responding to initiation of a near field RF communication by another near field RF communicator but not of initiating a near field RF communication with another near field RF communicator. Hence NFC communicators can act as both RFID transceivers and RFID transponders and are able to communicate with other NFC communicators, RFID transceivers and RFID transponders.
In addition NFC communicators may be associated with or comprised within or attached to certain peripheral devices, for example SIM cards (e.g. UICC), Secure Elements, memory devices (for example MCU, RAM, ROM and non-volatile memory), display driver or other drivers. During operation the NFC communicator must also be able to communicate with and transfer data to and from such peripheral device.
There are several standards in existence which set out certain communication protocols and functional requirements for RFID and near field RF communications. Examples are ISO/IEC 14443, ISO 15693, ISO/IEC 18092 and ISO/IEC 21481.
NFC communicators may be comprised within a larger device, NFC communications enabled devices. Examples include mobile telephones, PDAs, computers, smart cards. When comprised within such NFC communications enabled devices the NFC communicator must be able to transfer data to and from the larger device and to and from any peripheral devices (including interface systems, such as the single wire protocol) associated with such larger device.
NFC communicators and NFC communications enabled devices will usually have a power supply, for example a battery or fuel cell. Where the NFC communicator forms part of an NFC communications enabled device the power supply may be derived from the host or larger device, for example the mobile phone battery. Likewise power may be derived from a power supply provided by an attached or linked peripheral device (including interface systems such as the single wire protocol). This power supply is referred to as the primary or main power supply below. Due to the variety of uses to which NFC communicators may be put there is a need for such NFC communicators to be able to operate when the primary power supply is too low to provide sufficient power for the NFC communicator or is not present. For example the battery in a mobile phone may have been removed for charging, in which case the battery supply will not be available to an NFC communicator comprised within the mobile phone. An example of where the NFC communicator may require a power supply may be where the NFC communicator is designed to act as a transport ticket. A person will need to be able to use the transport ticket even when the battery in the mobile phone is low or depleted and thus the NFC communicator needs an alternative power source. In addition and unlike a passive transponder (which requires a derived power supply to operate) the NFC communicator needs to derive sufficient power to additionally power any peripheral device or host device or parts of such devices required for operation of the NFC communicator. For example where the NFC communicator is transferring secure data relating to payment to another NFC communicator (for example where such secure data is held on a secure element), it will require sufficient power not only to transfer the data but to power the secure element and to communicate with the secure element.
The provision of alternative power supplies (for example an additional battery) is expensive and can take up significant real estate within the NFC communicator or NFC communications enabled device. The alternative is a system which derives sufficient power from a received field to power the NFC communicator and any other functions within the NFC communications enabled device or peripheral device which must be powered for the NFC communicator to operate and communicate the required data. However in the latter case the level of received field cannot be guaranteed, nor can the time which the NFC communicator will be in that received field and able to derive power.